Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason.

Experience does not err. Only your judgments err by expecting from her what is not in her power.

For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.

I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do.

Human subtelty will never devise an invention more beautiful, more simple or more direct than does Nature, because in her inventions, nothing is lacking and nothing is superfluous.

Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.

As a well-spent day brings happy sleep, so a life well spent brings happy death.

He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast.

While I thought that I was learning how to live, I have been learning how to die.